• Journal of the Society of Naval Architects of Korea
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• v.34 no.3
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• pp.1-8
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• 1997

Internal solitary waves between two-stratified fluid layers are examined. Hamilton's principle is used to derive a governing equation. The wave speed-wave height relation is obtained and this agrees well with the experiment. The wave profiles obtained also agree well with the experimental result. There exist minimum and maximum wave speeds depending on the depth ratio and the density ratio of two layers. The KdV equation overpredicts the wave speed for a given wave height and underpredict the wave height for a given wave speed.

• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.2053-2060
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• 2005

The unsteady Couette flow of an electrically conducting, V1SCOUS, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer taking the Hall effect into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1675-1683
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• 1995

A numerical study of the fluid flow and heat transfer characteristics of the two-dimensional impingement jet with a confinement plate has been carried out. The fluid flow was calculated by solving the full Navier-Stokes equation. In doing that, the well known SIMPLER algorithm was used and the trouble making convection term was discretized according to QUICKER scheme. The energy equation was simply solved by using the SOR method. For the Reynolds number of 10000, two channel heights, say 1.5 and 3.0 times the jet exit width, and two thermal boundary conditions constant wall temperature and constant wall heat flux were considered. Discrete heat sources were flush mounted along the impingement plate at a distance of 0, 2, 3, 4, 5, 6, 10, 12, times the jet exit width from the stagnation point. The length of each heat source is 4 times the jet exit width long. The Nusselt number averaged over each heat source was compared with experiment. Comparison shows that both calculations and experiment have the secondary peak of Nusselt number at downstream of stagnation point, even though there is a little quantitative difference in between. The difference is believed due to abscure thermal boundary condition in experiment and also accuracy of turbulence model used. The secondary peak is shown to be caused by rigorous turbulent flow motion generated as the wall jet flow is retarded and developes into the channel flow without flow reversal.

• Structural Engineering and Mechanics
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• v.21 no.6
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• pp.635-658
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• 2005

The possibility of detecting a crack in L-shaped pipes filled with fluid based on measurement of transverse natural frequencies is examined. The problem is solved by representing the crack by a massless rotational spring, simulating the out-of-plane transverse vibration only without solving the coupled torsional vibration and using the transfer matrix method for solution of the governing equation. The theoretical solutions are verified by experiments. The cracks considered are external, circumferentially oriented and have straight front. Pipes made of aluminium and mild steel are tested with water as internal fluid. Crack size to pipe thickness ratio ranging from 0.20 to 0.57 and fluid (gauge) pressure in the range of 0 to 10 atmospheres are examined. The rotational spring stiffness is obtained by an inverse vibration analysis and deflection method. The details of the two methods are given. The results by the two methods are presented graphically and show good agreement. Crack locations are also determined by the inverse analysis. The maximum absolute error in the location is 13.80%. Experimentally determined variation of rotational spring stiffness with ratio of crack size to thickness is utilized to predict the crack sizes. The maximum absolute errors in prediction of crack size are 17.24% and 16.90% for aluminium and mild steel pipes respectively.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2005-2011
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• 2003

Introducing the interfacial pressure jump terms based on the surface tension into the momentum equations of two-phase two-fluid model, the system of governing equations is turned mathematically into the hyperbolic system. The eigenvalues of the equation system become always real representing the void wave and the pressure wave propagation speeds as shown in the previous manuscript. To solve the interfacial pressure jump terms with void fraction gradients implicitly, the conventional semi-implicit method should be modified as an intermediate iteration method for void fraction at fractional time step. This advanced semi-implicit method (ASIM) then becomes stable without conventional additive terms. As a consequence, including the interfacial pressure jump terms with the advanced semi-implicit method, the numerical solutions of typical two-phase problems can be more stable and sound than those calculated exclusively by using any other terms like virtual mass, or artificial viscosity.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.5
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• pp.548-553
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• 2015

The conventional ejector-diffuser system makes use of high pressure primary stream to propel the secondary stream through pure shear action for the purposes of transport or compression of fluid. It has been widely used in many industrial applications such as seawater desalination, solar refrigeration, marine engineering, etc. The present study is performed numerically to study the performance of a two-stage ejector-diffuser system. The detailed flow phenomenon of the ejector-diffuser system has been critically predicted by means of the numerical approach using compressible Reynolds averaged Navier-Stokes (RANS) equations. The axi-symmetric supersonic ejector-diffuser flow has been solved by a fully implicit finite volume scheme with a two-equation k-omega turbulence model. The numerical results are validated with existing experimental data. Detailed flow physics and their contributions on ejector performance are detected to compare both single-stage and two-stage ejectors. The performance improvement on the ejector-diffuser system is discussed in terms of the mass flux ratio and the coefficient of power.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.14 no.2
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• pp.118-124
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• 1985

The motion of a fluid in the closed annular cavity formed by two concentric vertical cylinders with externally finned tube has been analysed by a numerical solutions of the equation of momentum and energy. For the calculation procedure, the fluid is assumed to have constant thermo-dynamic and transporties except for the density, which is temperature-dependent in the buoyancy term of the vertical momentum equation (Boussinesq approximation). The govern ins equations for velocity and temperature are solved by a finite difference technique which incoorporates a scheme for treating the coupled variables. Results are presented for a range of the Rayleigh number and for various values of the fin height and the number of fins.

• Journal of the Korean Society of Visualization
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• v.2 no.2
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• pp.8-15
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• 2004

With all the recent progresses in computer hardware and software technology, the animation of fluids in real-time is still among the most challenging issues of computer graphics. The fluid animation is carried out in two steps - the physical simulation of fluids immediately followed by the visual rendering. The physical simulation is usually accomplished by numerical methods utilizing the particle dynamics equations as well as the fluid mechanics based on the Navier-Stokes equations. Particle dynamics method is usually fast in calculation, but the resulting fluid motion is conditionally unrealistic. The methods using Navier-Stokes equation, on the contrary, yield lifelike fluid motion when properly conditioned, yet the complexity of calculation restrains this method from being used in real-time applications. This article presents a rapid fluid animation method by using the continuum-based fluid mechanics and the enhanced particle dynamics equations. For real-time rendering, pre-integrated volume rendering technique was employed. The proposed method can create realistic fluid effects that can interact with the viewer in action, to be used in computer games, performances, installation arts, virtual reality and many similar multimedia applications.

• Journal of Biomedical Engineering Research
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• v.5 no.2
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• pp.161-166
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• 1984

In this paper, we describe an effective technique for computing the steady-state motion in a two-dimensional cochlear model. With the cochlear fluid assumed incompressible and invisid, the problem reduces to solving an integral equation for a region with yielding boundary. Using the conformal mapping, Jacobian elliptic function and hyperbolic function, a pair of second-order differential equation is derived. What we will show in this paper is that by appropriately transforming integral equation, the same computation can be performed with comparable accuracy in a short time.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.2
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• pp.103-121
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• 2015

In this paper, we briefly review and describe a projection algorithm for numerically computing the two-dimensional time-dependent incompressible Navier-Stokes equation. The projection method, which was originally introduced by Alexandre Chorin [A.J. Chorin, Numerical solution of the Navier-Stokes equations, Math. Comput., 22 (1968), pp. 745-762], is an effective numerical method for solving time-dependent incompressible fluid flow problems. The key advantage of the projection method is that we do not compute the momentum and the continuity equations at the same time, which is computationally difficult and costly. In the projection method, we compute an intermediate velocity vector field that is then projected onto divergence-free fields to recover the divergence-free velocity. Numerical solutions for flows inside a driven cavity are presented. We also provide the source code for the programs so that interested readers can modify the programs and adapt them for their own purposes.